Under the Patient Protection and Affordable Care Act (ACA), many veterans will gain new insurance options to finance their use of non-VA care. More choices about insurance coverage and providers can improve patients' access to health care and timely use of services. Since ACA may ultimately impact quality of care, workforce planning, and enrollment in VA medical centers, it is critical for VA providers and policymakers to understand the potential impact of new insurance alternatives on the demand for VA care. The primary objective of this project is to examine dual use among nonelderly VA enrollees who acquire Medicaid coverage since states are adopting Medicaid expansion plans, among other options, to cover previously uninsured residents. This proposed study will: 1) assess the impact of new Medicaid coverage on use of VA and Medicaid care and health care spending, both overall and separately for specific types of services, for nonelderly VA enrollees between CY2006 and CY2010; 2) determine how the use, costs, and reliance of VA care following Medicaid coverage varies by patient demographic and clinical characteristics and state Medicaid policy factors; and 3) estimate the total population changes in VA utilization and costs at potential levels of Medicaid coverage among currently uninsured VA enrollees. We will use VA-Medicaid linked files to obtain VA and Medicaid utilization and costs for inpatient, outpatient, and pharmacy care. After identifying nonelderly veterans newly enrolled in Medicaid, we will observe patients' utilization and costs of VA one year prior to Medicaid enrollment and their VA and Medicaid utilization for two years following Medicaid enrollment. Outpatient visits will be estimated separately for treatment of mental health and substance abuse disorders and all other care. Inpatient stays will be estimated separately for medical/surgical and psychiatric care. Mean utilization and costs per patient will be summarized for total care provided by VA and proportion of VA care (reliance) by Medicaid enrollment status. We will compare the estimates separately for those enrolled and not enrolled in Medicaid. Multivariable, multilevel regression models will be developed to predict the total VA utilization, costs, and reliance adjusting for Medicaid enrollment and all patient and state factors. Using the estimates of changes in VA utilization and costs after Medicaid enrollment, we will model population changes in VA utilization and costs at different potential levels of Medicaid coverage among currently uninsured, nonelderly VA enrollees. Final results will be provided to our operational partners to incorporate into forecasting models of demand and costs of VA care for planning and policy deliberation.